System and method for determining a location for a mobile device

ABSTRACT

A system for determining a location for a mobile communication device includes a plurality of taps, a multiplexer, and a link aggregator. Each tap includes a pair of connectors that couple to a communication link of a radio access network inline and pass between them a signal received over the communication link. Each tap also includes a multiplexer connector that couples to a multiplexer and a cable connecting the multiplexer connector to the inline connectors. The tap replicates signals passing between the inline connectors and propagates the replicated signals to the multiplexer connector. The multiplexer receives, from each tap, signals replicated by that tap, extracts location data from the received signals, and transmits the location data to a link aggregator. The link aggregator receives the location data from the multiplexer and determines a location for one of the mobile devices based on the received location data.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to mobile phones, and moreparticularly to locating mobile devices.

BACKGROUND OF THE INVENTION

Mobile communication devices have become ubiquitous in recent years.Countless individuals communicate with one another using mobilecommunication devices and, as a result, many people have access to acommunication device at all times. This increased availability has ledto greater safety for pedestrians, motorists, and other individuals insituations where they do not have access to conventional landlinetelephones.

Unlike with conventional landline telephones, however, there is no afixed association between a mobile communication device and itslocation. As a result, in emergency situations, emergency serviceproviders cannot determine the location of a caller calling on a mobiledevice based simply on the phone number associated with the device. Ifthe caller becomes incapacitated during the call, disconnected, orotherwise prevented from communicating with the emergency serviceprovider, the emergency service provider may be unable to locate andassist the caller. Furthermore, even if the caller is able tocommunicate with the emergency service provider, in many cases thecaller may be unable to determine his or her location. As a result,there is an increasing need for effective techniques to establish thelocation of mobile communication devices.

However, the surge in mobile communications has led to increasinglycomplex communication networks, as service providers struggle toaccommodate the ever-growing number of users. As a result of thiscomplexity, interfacing with and extracting information from mobilecommunication networks has likewise increased in complexity. Componentsand systems designed to interoperate with mobile communication deviceshave become more expensive and complicated, hampering the developmentand implementation of solutions for locating mobile communicationdevices.

SUMMARY OF THE INVENTION

In accordance with the present disclosure, certain disadvantages andproblems associated with mobile communication have been substantiallyreduced or eliminated. In particular, an apparatus and method fordetermining the location of a mobile communication device is provided.

In accordance with one embodiment of the present disclosure, a systemfor determining a location for a mobile communication device includes aplurality of taps, a multiplexer, and a link aggregator. Each tapincludes a pair of connectors that couple inline to a communication linkof a radio access network and pass between them a signal received overthe communication link. Each tap also includes a multiplexer connectorthat couples to a multiplexer and a cable connecting the multiplexerconnector to the inline connectors. The tap replicates signals passingbetween the inline connectors and propagates the replicated signals tothe multiplexer connector. The multiplexer receives, from each tap,signals replicated by that tap, extracts location data from the receivedsignals, and transmits the location data to a link aggregator. The linkaggregator receives the location data from the multiplexer anddetermines a location for one of the mobile devices based on thereceived location data.

In accordance with another embodiment of the present invention, a methodfor determining a location for a mobile communication device includesreceiving, at each of a plurality of taps, a signal transmitted over acorresponding communication link of a radio access network. Each of thetaps comprises a pair of connectors coupled inline to the correspondingcommunication link. The method also includes passing the signal receivedat each tap between the corresponding pair of connectors and replicatingthe signal received at each tap on a multiplexer connector of the tap.Additionally, the method includes receiving the signal replicated byeach of the taps at a multiplexer coupled to the taps and extractinglocation data from the received signals. The location data is associatedwith one or more mobile devices operating in a geographic area served bythe radio access network. The method further includes transmitting thelocation data over a data network in accordance with an internetprotocol (IP) to a link aggregator and determining, at the linkaggregator, a location for one of the mobile devices based on locationdata received from the multiplexer.

Important technical advantages of certain embodiments of the presentinvention include determining a location of a mobile device using aninexpensive, compact system with reduced complexity. Particularembodiments may be capable of determining locations independent of thecommunications system on which the caller is communicating.Additionally, particular embodiments allow extraction of informationrelevant to the location of the mobile communication device withoutestablishing additional communication links between the extractingapparatus and downstream nodes in the communication network. Otheradvantages of the present invention will be readily apparent to oneskilled in the art from the following figures, descriptions, and claims.Moreover, while specific advantages have been enumerated above, variousembodiments may include all, some, or none of the enumerated advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsadvantages, reference is now made to the following description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates a mobile communication system and an intercept systemaccording to one embodiment of the present disclosure;

FIG. 2 is a block diagram illustrating in greater detail a tap that maybe used in particular embodiments of the intercept system shown in FIG.1;

FIG. 3 is a block diagram illustrating in greater detail a multiplexerthat may be used in particular embodiments of the intercept system; and

FIG. 4 is a flow chart illustrating example operation of a particularembodiment of the intercept system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a mobile communication system 10 in which anintercept system 20 has been installed. Mobile communication system 10provides mobile communication service to a plurality of mobilecommunication devices 50. Intercept system 20 extracts data frominformation communicated between various elements of mobilecommunication system 10 and uses the extracted data to determinelocations of mobile devices 50. In particular embodiments, interceptsystem 20 is capable of transparently extracting and aggregatinglocation data transmitted within mobile communication system 10 and mayprovide a cost-effective solution for locating mobile devices 50 servedby mobile communication system 10.

Mobile communication system 10 provides mobile communication service tomobile devices 50 operating within a geographic area associated withmobile communication system 10. Mobile communication system 10 includesan access network 30 and a core network 40. Mobile communication system10 may support communication of any suitable type and/or in accordancewith any appropriate communication standards including, but not limitedto, any second generation (“2G”), third generation (“3G”), or fourthgeneration (“4G”) standards, or any suitable transitional generationstandards (e.g., 2.5G, 2.75G, 3.5G, and 3.9G). Particular embodiments ofmobile communication system 10 may support communications in accordancewith, for example, Global System for Mobile Communications (GSM),CDMAOne, General Packet Radio Service (GPRS), Enhanced Data rates forGSM Evolution (EDGE), CDMA2000, Integrated Digital Enhanced Network(iDen), Universal Mobile Telecommunications System (UMTS), Wideband CodeDivision Multiple Access (WCDMA), Long Term Evolution (LTE), and/orWorldwide Interoperability for Microwave Access (WiMAX) communicationstandards.

Access network 30 communicates wirelessly with mobile devices 50 andserves as an interface between mobile devices 50 and core network 40.Access network 30 may represent or include a radio access network and/orany elements responsible for providing a radio or air interface for corenetwork 40. For example, in the illustrated embodiment, access network30 includes base stations 32 and radio controllers 34.

Base stations 32 communicate wirelessly with mobile devices 50 tofacilitate mobile communication for mobile devices 50. Base stations 32may include any appropriate elements to communicate with mobile devices50 and to interface mobile devices 50 with core network 40. For example,depending on the communications standards supported by access network 30and core network 40, each base station 32 may represent or include aconventional base station, a Node B, an evolved Node B (eNode B), aradio base station (RBS), or any other suitable element capable ofcommunicating with mobile devices 50 wirelessly.

Radio controllers 34 control the operation of base stations 32 andinteract with appropriate elements of core network 40. Radio controllersmay include any appropriate elements to manage the operation of basestations 32. In particular embodiments, radio controllers 34 may beresponsible for managing radio channels used by base stations 32,managing handoffs between base stations 32, concentrating communicationchannels transmitted by base stations 32, and/or otherwise managing theoperation and interoperation of base stations 32 and interfacing basestations 32 with core network 40. For example, depending on thecommunications standards supported by access network 30 and core network40, radio controllers 34 may each represent or include a base stationcontroller (BSC), a radio network controller (RNC), or any othersuitable collection of hardware and/or software appropriate forcontrolling base stations 32.

Core network 40 routes voice and/or data communicated by mobile devices50 from access network 30 to other mobile devices 50 or to othercommunication devices coupled to core network 40 through landlineconnections or through other networks. In particular embodiments, corenetwork 40 may include a backbone network and any backhaul elementsconnecting access network 30 to the backbone network. Core network 40may support any appropriate standards or techniques for routing suchcommunications. For example, in embodiments of mobile communicationsystem 10 that support GSM or UMTS, core network 40 may represent aMobile Application Part (MAP) core network, while in embodiments ofmobile communication system 10 that support CDMA2000, core network 40may represent an IS-41 core network. Additionally, core network 40 mayalso be responsible for aggregating communication for longhaultransmission, authenticating users, managing user mobility, providingcall control, billing, or other functionality associated with providingcommunication services to mobile devices 50. In particular embodiments,core network 40 may include separate subnetworks for circuit-switchedand packet-switched communication. For example, in embodiments thatsupport GSM communication, core network 40 may include a networkswitching subsystem and any mobile switching centers (MSCs) forproviding circuit-switched services, as well as a GPRS core network andany Gateway GPRS Support Nodes (GGSNs) and Serving GPRS Support Nodes(SGSNs) for providing packet-switched services. In general, however,core network 40 may include any components suitable for routing andsupporting voice and/or data communications for mobile devices 50.

Intercept system 20 extracts information from appropriate communicationlinks within mobile communication system 10 and, based on the extractedinformation, determines locations for particular mobile devices 50served by mobile communication system 10. In particular embodiments,intercept system 20 may be capable of collecting information frommultiple base stations 32 and aggregating the collected information,thereby permitting intercept system 20 to determine and store locationsfor several different mobile devices 50 located throughout thegeographic area served by mobile communication system 10. Althoughintercept system 20 may include any appropriate elements suitable toprovide the described functionality, the illustrated embodiment ofintercept system 20 includes a plurality of taps 22, a plurality ofmultiplexers 24, and a link aggregator 26.

Taps 22 couple to base stations 32, radio controllers 34, or othersuitable elements of access network 30 and replicate informationcommunicated over communication links of mobile communication system 10.Taps 22 may, in various embodiments, couple to such links as thosebetween mobile devices 50 and base stations 32, base stations 32 andradio controllers 34, or between radio controllers 34 and core network40. In particular embodiments, taps 22 are passive elements thatreplicate information from the appropriate links or interfaces bysplitting signals passing through taps 22 without altering theduplicated signals from the perspective of the elements transmitting andreceiving the relevant signals. This may allow taps 22 to replicate therelevant signals in a manner that is transparent to the transmitting andreceiving elements. As a result, taps 22 may be able to avoid performinghandshakes with upstream or downstream elements, maintaining protocolstacks, and/or providing other functionality required of nodescommunicating within access network 30 or core network 40. Consequently,particular embodiments of taps 22 may be designed and manufactured withless complexity and cost than if taps 22 operated as fully functionalnodes within access network 30 or core network 40. Taps 22 may representany appropriate combination of hardware and/or software suitable toprovide the described functionality. The structure and operation of aparticular embodiment of tap 22 is described in greater detail belowwith respect to FIG. 2.

Multiplexers 24 are each associated with a plurality of taps 22 andreceive signals replicated by their associated taps 22. Multiplexers 24process information conveyed by the signals received from taps 22 andprepare the information for transmission to link aggregator 26. Althoughmultiplexers 24 may be designed to couple to any suitable number of taps22, particular embodiments of intercept system 20 utilize multiplexers24 configured to couple to all of the taps 22 installed at a particularbase station 32 or radio controller 34. Although multiplexers 24 mayrepresent any appropriate combination of hardware and/or softwaresuitable to provide the described functionality, particular embodimentscomprise field-programmable gate arrays (FPGA) programmed to provideappropriate processing of the signals received from taps 22. Thestructure and operation of a particular embodiment of multiplexer 24 isdescribed in greater detail below with respect to FIG. 3.

Link aggregator 26 determines locations of various mobile devices 50receiving service from mobile communication system 10 based oninformation received from multiplexers 24. Although in the illustratedembodiment multiplexers 24 connect to link aggregator 26 through aseparate data network (not shown), link aggregator 26 may connect tomultiplexers 24 over a separate data network, through core network 40,via direct connections to multiplexers 24, or in any other appropriatemanner. Link aggregator 26 may also represent any appropriatecombination of software and/or hardware suitable to provide thedescribed functionality. In particular embodiments, link aggregator 26represents a personal computer (PC) or server capable of receivinginternet protocol (IP) transmissions from multiplexers 24. For example,in particular embodiments, link aggregator 26 represents a Sun X4270server suitably programmed to provide the described functionality.

In operation, mobile communication system 10 provides telecommunicationservice to mobile devices 50. For example, in the illustratedembodiment, base stations 32 communicate wirelessly with mobile devices50 to facilitate the transmission of information between mobile devices50 and core network 40. Radio controllers 34 manage handovers betweenbase stations 32 and otherwise coordinate interaction of associated basestations 32. Core network 40 transports voice and/or data betweenindividual base stations 32 and between base stations 32 and otherelements of mobile communication system 10, such as wirelinecommunication devices.

Intercept system 20 extracts information transmitted between mobiledevices 50 and mobile communication system 10 and, based on theextracted information, determines locations of the relevant mobiledevices 50. In particular embodiments, intercept system 20 may becapable of collecting information from multiple base stations 32 and/orradio controllers 34 and aggregating the collected information, therebypermitting intercept system 20 to determine locations for severaldifferent mobile devices 50 spread throughout the geographic area servedby mobile communication system 10. Furthermore, intercept system 20 may,in particular embodiments, be capable of extracting the relevantinformation from mobile communication system 10 transparently,permitting intercept system 20 to be installed and operated with reduceddifficulty and expense.

For example, as noted above, the illustrated embodiment of interceptsystem 20 includes a plurality of taps 22, a plurality of multiplexers24, and a link aggregator 26. Taps 22 are coupled to appropriatecommunication links in mobile communication system 10, such as thosebetween mobile devices 50 and base stations 32, base stations 32 andradio controllers 34, or between radio controllers 34 and core network40. Taps 22 replicate the signals transmitted in mobile communicationsystem 10. As one example, in embodiments of mobile communication system10 that support GSM, taps 22 may be coupled to either a BTS (serving asa base station 32) or a BSC (serving as a radio controller 34) andreplicate signals transmitted over the Abis interface connecting the BTSand BSC or taps 22 may be coupled to the BSC (serving as radiocontroller 34) or an MSC (within core network 40) and replicate signalstransmitted over the A interface connecting the BSC and MSC. As anotherexample, in embodiments of mobile communication system 10 that supportUMTS, taps 22 may be coupled to either a NodeB (serving as a basestation 32) or an RNC (serving as a radio controller 34) and replicatessignals transmitted over the Iub interface connecting the NodeB and theRNC. Similarly, taps 22 may be coupled to an RNC and replicate signalscommunicated over an Iur interface (with another RNC), an Iu-CSinterface (with an MSC in core network 40), or an Iu-PS interface (withan SGSN in core network 40). In general, various embodiments of taps 22may be capable of coupling to any appropriate element of access network30 and replicating signals on any appropriate communication linksassociated with access network 30.

Each tap 22 is coupled to a multiplexer 24 to which the signalsreplicated by that particular tap 22 are transmitted. For example, inparticular embodiments, each tap 22 replicates a set of E1transmit/receive signal pairs that propagate to the multiplexer 24associated with that tap 22. Multiplexers 24 receive signals from aplurality of taps 22 and process these signals for transmission to linkaggregator 26. Multiplexers 24 may process replicated signals in anyappropriate manner to facilitate the transmission of relevantinformation to link aggregator 26. In particular embodiments,multiplexer 24 conditions signals received from taps 22 for use bymultiplexer 24 or link aggregator 26. For example, in particularembodiments, multiplexers 24 amplify the received signals and performnoise filtering on the resulting output. Multiplexers 24 may also detectsynchronization data in the received signals to permit synchronoustransfer of the signals to link aggregator 26. Furthermore, after anyappropriate conditioning of the received signals, multiplexers 24 mayformat information communicated by the received signals to facilitatetransmission of the information to link aggregator 26. For example,multiplexers 24 may aggregate information received from taps 22 and thenform data frames containing the aggregated information for synchronoustransmission to link aggregator 26. Multiplexers 24 may then packetizeand encapsulate these frames for transmission to link aggregator 26 overan internet protocol (IP)/transfer control protocol (TCP) connection.

Additionally, multiplexers 24 may extract information from the receivedsignals based on the location calculations to be completed by interceptsystem 20. For example, in particular embodiments, a multiplexer 24 mayfilter information (such as Mobile Subscriber ISDN Numbers (MSISDNs),International Mobile Subscriber Identities (IMSIs), or Temporary MobileSubscriber Identities (TMSIs)) identifying mobile devices 50 associatedwith the signals received by multiplexer 24, information identifying abase station 32 (e.g., a cell identifier) with which these mobiledevices 50 are communicating, information identifying a particulargeographical area in which these mobile devices 50 are currentlyoperating (e.g., a cell sector or antenna identifier), and/or any otherappropriate information to be used by link aggregator in determining thelocation of mobile devices 50. Alternatively, multiplexers 24 may beconfigured to format all information received from taps 22 fortransmission and transmit all such information to link aggregator 26 forprocessing by link aggregator 26 itself.

After any appropriate conditioning, filtering, or other processing,multiplexers 24 transmit appropriate information from the receivedsignals to link aggregator 26. Link aggregator 26 receives thetransmitted information and determines locations of mobile devices 50served by mobile communication system 10 based on the transmittedinformation and/or appropriate information maintained by link aggregator26. In particular embodiments, link aggregator 26 may itself storeadditional data that link aggregator 26 uses in making locationdeterminations, such as locations of base stations 26 and historicallocation information for mobile devices 50. Depending on theconfiguration of intercept system 20, link aggregator 26 may determinelocations on an ongoing basis or, alternatively, in response to locationrequests from an operator or other elements of intercept system 20.

Link aggregator 26 may utilize any suitable techniques for determining alocation for a particular mobile device 50 and may determine a locationof any appropriate form and precision. The determined location mayrepresent an absolute location for the relevant mobile device 50 (e.g.,a latitude and longitude of the mobile device 50) or a relativelocation, reflecting a distance between the mobile device 50 and anotherlocation, such as a known landmark. Furthermore, the determined locationmay reflect the location of the relevant mobile device 50 in anysuitable manner including, but not limited to, by providing an estimateof the location of the mobile device 50, a prediction of the location ofthe mobile device 50, or the location of some other object associatedwith the mobile device 50 (e.g., a base station 32 serving the mobiledevice 50). For example, in particular embodiments, link aggregator 26may determine a location of a particular mobile device 50 byidentifying, based on information received from multiplexers 24 (e.g., aCell Global Identity (CGI)), a cell in which the mobile device iscurrently communicating and determining, based on stored information, alatitude and longitude of the cell's center point or of a base station32 serving that cell. As another example, link aggregator 26 maydetermine a location for the mobile device 50 based on timinginformation (e.g., a Round Trip Time (RTT) or Timing Advance (TA)calculation) or signal strength information (e.g., a Received SignalStrength Indication (RSSI) measurement) associated with signalstransmitted to or received from the mobile device 50 by one or more basestations 32. Link aggregator 26 may use this timing or signal strengthinformation, along with stored locations for the relevant base stations32 or their associated cells, to determine a location for the relevantmobile device 50. In general, link aggregator 26 may utilize anyappropriate information and techniques to determine any suitable form oflocation for the relevant mobile device 50. Moreover, in particularembodiments, link aggregator 26 may make the location determination byusing information received from multiplexers 24 to request locationinformation associated with the relevant mobile device 50 fromappropriate elements of access network 30, such as a serving mobilelocation center (SMLC).

Depending on the functionality being implemented by a particularembodiment of intercept system 20, link aggregator 26 may then use thedetermined location to complete additional operations. For example, inparticular embodiments, intercept system 20 may be used by an emergencyservice provider to determine the location for a mobile device user. Insuch embodiments, intercept system 20 may receive location requests froma dispatcher for the emergency service provider, and link aggregator 26may determine the location of a particular mobile device 50 in responseto each of these requests. After determining a location for the relevantmobile device 50, link aggregator 26 may then transmit the location to acomputer or other device for display to the dispatcher. As anotherexample, in particular embodiments, link aggregator 26 may determinelocations for mobile devices 50 on an ongoing basis and store thedetermined locations in memory for some subsequent use, such asmonitoring usage patterns of mobile device users. In general, interceptsystem 20 may utilize the determined location for network optimization,traffic management, zone-based billing, targeted advertising, lawenforcement efforts, or any other suitable purpose.

Thus, particular embodiments of intercept system 20 provide acost-effective, low-complexity solution for determining the location ofa large number of mobile devices 50 in real-time. By utilizing linkaggregator 26, in part or in whole, to make these locationdeterminations, intercept system 20 may reduce the signaling that wouldoccur on access network 30 and core network 40 to complete suchdeterminations using conventional techniques. Additionally, offloadingthese determinations to link aggregator 26 may reduce less optimal useof processing resources by other elements of mobile communication system10. As a result, certain embodiments of intercept system 20 may behighly scalable and capable of supporting a mobile communication system10 that covers an extensive geographic area and services a significantnumber of mobile devices 50. Moreover, because particular embodiments ofintercept system 20 can operate with base stations 32, radio controllers34, and mobile devices 50 that utilize a wide variety of communicationstandards, intercept system 20 may provide a flexible, robust solutionfor location-based services. Consequently, particular embodiments ofintercept system 20 may provide numerous benefits. Specific embodiments,however, may provide some, none, or all of these benefits.

FIG. 2 illustrates in greater detail a particular embodiment of tap 22that may be utilized in intercept system 20. As shown in FIG. 2, tap 22includes a first inline connector 202, a second inline connector 204, acable 206, and a multiplexer connector 208.

First inline connector 202 and second inline connector 204 couple tap 22to an interface or link within access network 30 or between accessnetwork 30 and core network 40. First inline connector 202 and secondinline connector 204 are directly connected to one another or arecoupled to each other by way of a conductive path running between inlineconnectors 202 and 204. As a result, a signal received on one of inlineconnectors 202 and 204 passes to the other and to any component attachedto the other connector 202 or 204. Consequently, particular embodimentsof tap 22 may be connected to access network 30 inline with a particularcommunication link. Signals communicated over the relevant communicationlink will propagate through tap 22 without downstream or upstreamcomponents on the communication link detecting the presence of tap 22and/or changes in transmitted or received signals resulting from tap 22.

As discussed above with respect to FIG. 1, tap 22 may be designed forattachment to a number of different communication links. Thus, firstinline connector 202 and second inline connector 204 may represent anyconnectors suitable for attachment to the relevant communication linksand/or their associated interfaces. In particular embodiments, inlineconnectors 202 and 204 comprise D-subminiature connectors of anappropriate size and layout for coupling to the relevant communicationlinks. For example, in particular embodiments of intercept system 20that support GSM, tap 22 may attach to a BSC via a 44-pin connectorassociated with the BSC's Abis interface. In such embodiments, firstinline connector 202 and second inline connector 204 may represent,respectively, male and female 44-pin DB-44 connectors. When installed,one of the inline connectors 202 or 204 will couple to the Abisconnector of the BSC, while the other inline connector 202 or 204 willcouple to a cable associated with the Abis interface.

Cable 206 couples multiplexer connector 208 to first inline connector202 and second inline connector 204. Cable 206 may represent anyconductive element capable of forming a conductive path betweenmultiplexer connector 208 and inline connectors 202 and 204 andpropagating signals passing between inline connectors 202 and 204 tomultiplexer connector 208. In particular embodiments, cable 206comprises a twisted pair ribbon cable.

Multiplexer connector 208 provides a conductive connection that can becoupled to a multiplexer 24. Signals received at first inline connector202 or second inline connector 204 are replicated on multiplexerconnector 208 for use by multiplexer. In particular embodiments,multiplexer connector 208 is responsible for carrying all signalsreceived at inline connectors 202 and 204 to multiplexer 24 and, as aresult, multiplexer connector 208 comprises a connector similar toinline connectors 202 and 204. Thus, in particular embodiments,multiplexer 208 comprises a D-subminiature connector of a similar sizeand layout to inline connectors 202 and 204.

In operation, tap 22 may be installed on an appropriate communicationlink within mobile communication system 10. First inline connector 202and second inline connector 204 may be connected inline on the relevantlink, while multiplexer connector 208 may be connected to a multiplexer24 associated with tap 22. Signals received on first inline connector202 pass to second inline connector, while signals received on secondinline connector 204 pass to first inline connector 202.

Additionally, signals passing through first inline connector 202 orsecond inline connector 204 in either direction are replicated onmultiplexer connector 208. Signals resulting from this replication carrythe same information as the signals received by tap 22 but, depending onthe configuration of tap 22, may differ in voltage, phase, or othercharacteristics. In particular embodiments, tap 22 performs thisreplication passively. For example, cable 206 may be connected directlyto inline connectors 202 and 204 or to a conductive path connectinginline connectors 202 and 204 so that signals passing between inlineconnectors 202 and 204 are split and propagate along cable 206 tomultiplexer connector 208. In alternative embodiments, tap 22 performsthis replication actively. For example, tap 22 may include a repeater orother element that replicates a received signal by transmitting aduplicate of the received signal to multiplexer connector 208. Inparticular embodiments, tap 22 may replicate received signals in amanner such that received signals passing through tap 22 do notexperience a substantial loss in signal level.

FIG. 3 is a block diagram showing in greater detail the contents ofmultiplexer 24 according to particular embodiments. As shown,multiplexer 24 includes a processor 302, a memory 304, a plurality oftap interfaces 306, a network interface 308, a conditioning module 310,a filtering module 312, and a formatting module 314.

Processor 302 may represent or include any form of processing component,including dedicated microprocessors, general-purpose computers, or otherdevices capable of processing electronic information. Examples ofprocessor 302 include field-programmable gate arrays (FPGAs),programmable microprocessors, digital signal processors (DSPs),application-specific integrated circuits (ASICs), and any other suitablespecific- or general-purpose processors. Although FIG. 3 illustrates,for the sake of simplicity, an embodiment of multiplexer 24 thatincludes a single processor 302, multiplexer 24 may include any numberof processors 302 configured to interoperate in any appropriate manner.For example, in particular embodiments, multiplexer 24 includes fourFPGAs each capable of receiving and processing twenty-four (24) full E1channels (i.e., forty-eight (48) separate transmit/receive connections).As a result, in such embodiments, multiplexer 24 may be capable ofprocessing ninety-six (96) full E1 channels (i.e., 192 separatetransmit/receive connections).

Memory 304 stores processor instructions, filter parameters, routinginformation, and/or any other data utilized by multiplexer 24 duringoperation. Memory 304 may comprise any collection and arrangement ofvolatile or non-volatile, local or remote devices suitable for storingdata, such as random access memory (RAM), read only memory (ROM),magnetic storage, optical storage, or any other suitable type of datastorage components. Although shown as a single element in FIG. 3, memory304 may include one or more physical components local to or remote frommultiplexer 24.

Tap interfaces 306 each couple multiplexer 24 to a tap 22 and receivereplicated signals from the corresponding tap 22. Although shown in FIG.3 as representing multiple separate components, tap interfaces 306 may,in particular embodiments, represent a single component capable ofconnecting to multiple different taps 22 and receiving signals from allsuch taps 22 simultaneously. If taps 22 include active components, tapinterfaces 306 may provide additional functionality to facilitatecommunication with such active components, such as control signaling andchannel setup.

Network interface 308 facilitates communication between multiplexer 24and link aggregator 26 or other components of intercept system 20 ormobile communication system 10 over a data network. Network interface308 may facilitate communication over portions of core network 40 orover a separate data network. In particular embodiments, networkinterface 308 includes or represents one or more network interface cards(NICs).

Conditioning module 310 conditions signals received from taps 22 forfurther processing by multiplexer 24 and transmission to link aggregator26. Conditioning module may amplify received signals, perform noisefiltering, isolate synchronization data in received signals, and/orperform any other appropriate conditioning of signals received from taps22.

Filtering module 312 receives signals transmitted by taps 22 after anyappropriate conditioning has been completed and extracts information tobe transmitted to link aggregator 26. Depending on the locationtechniques utilized by intercept system 20, filtering module 312 mayfilter out cell identifiers, mobile device identifiers, timinginformation, signal strength indicators, and/or any other informationthat may be used in determining a location. As noted above, alternativeembodiments of multiplexer 24 may transmit all information received fromtaps 22 to link aggregator 26 and such embodiments may not perform anyfiltering of the signals received from taps 22.

Formatting module 314 formats information for transmission to linkaggregator 26 through network interface 308. In particular embodiments,formatting module 314 may aggregate information communicated by signalsreceived from multiple different taps 22 and generate synchronous framescontaining the aggregated information. Additionally, in particularembodiments, multiplexer 24 communicates with link aggregator 26 via anIP/TCP communication link. In such embodiments, formatting module 314may packetize and encapsulate information carried by the receivedsignals and generate any necessary addresses or other header informationfor communicating the resulting packets to link aggregator 26.

In general, conditioning module 310, filtering module 312, andformatting module 314 may each represent any appropriate combination ofhardware and/or software suitable to provide the describedfunctionality. Additionally, tap modules 310-314 may collectivelyrepresent a single physical component or any appropriate number ofseparate physical components. In particular embodiments, modules 310-314represent, in part or in whole, software applications executing onprocessor 214.

In particular embodiments, the structural components of multiplexer 24can be attached to one or more chassis 316 for mounting in a standardnineteen-inch (“19”) or twenty-three-inch (“23”) electronic rack. As aresult, multiplexer 24 may represent a rack-mountable component that canbe inserted into standard equipment racks commonly used to housetelecommunications equipment in modern mobile communication systems,such as racks complying with EIA-310-D and/or EN 300 119. Thus,particular embodiments of multiplexer 24 can be easily integrated withexisting equipment in many types of mobile communication systems.Furthermore, in particular embodiments, the components used to providethe functionality described for multiplexer 24 can be fit on a singlechassis 316 or a collection of chassis 316 having relatively smallsizes. For example, a particular embodiment of multiplexer 24 capable ofcollecting information from up to 448 individual E1 links (or 224 E1transmit/receive pairs) can be formed from components attached to twochassis. The first chassis supports components for extractinginformation from received E1 signals and is three rack units (3U) insize. The second chassis supports components for generating andtransmitting frames of extracted information and is one rack unit (1U)in size. Thus, in such embodiments, 448 E1 links can be served by arack-mountable multiplexer 24 spanning a total of four rack units (4U)or less.

FIG. 4 is a flow chart illustrating example operation for a particularembodiment of intercept system 20. In particular, FIG. 4 illustratesexample operation for an embodiment of intercept system 20 thatdetermines locations for mobile devices 50 in response to requestsreceived from an emergency service provider. The steps illustrated inFIG. 4 may be combined, modified, or deleted where appropriate.Additional steps may also be added to the example operation.Furthermore, the described steps may be performed in any suitable order.

Operation in this example begins, at step 400, with link aggregator 26or another suitable element of intercept system 20 receiving a locationrequest from a dispatcher of an emergency service provider. Thislocation request may identify a particular mobile device 50 (e.g., byMSISDN) and include other information needed by link aggregator 26 todetermine a location for the identified mobile device 50. For example,in particular embodiments, link aggregator 26 may support HypertextTransfer Protocol (HTTP) and may receive an HTTP request from a client,such as a PC, operated by the dispatcher.

At an appropriate point before or after intercept system 20 receives thelocation request, intercept system 20 begins collecting information tobe used in locating mobile devices 50. As part of this process, one ormore taps 22 each receive, at step 410, a separate signal transmittedover a corresponding communication link of access network 30. As notedabove, in particular embodiments, taps 22 may each comprise a pair ofconnectors 202 and 204 coupled inline to the corresponding communicationlink. At step 420, the one or more taps 22 pass their respectivereceived signals between their pair of connectors 202 and 204.Additionally, at step 430, each of the taps 22 replicates the signal itreceived on a multiplexer connector 208 of that tap 22.

The replicated signals are received at a multiplexer 24 coupled to taps22 at step 440. Intercept system 20 may include multiple multiplexers24, and each multiplexer 24 may be coupled to and receive replicatedsignals from a different set of taps 22. At step 450, the one or moremultiplexers 24 extract location data from signals received from taps22. This location data is associated with one or more mobile devices 50operating in a geographic area served by access network 30 and maycomprise any data used by intercept system 20 to determine locations ofthe relevant mobile devices 50. Examples of location data may include,but are not limited to, cell identifiers, device identifiers, timinginformation, and/or signal strength measurements.

After any appropriate formatting of the extracted location data,multiplexers 24 transmit the extracted location data to link aggregator26 over a data network at step 460. In particular embodiments,multiplexer 24 transmits the extracted location data to link aggregatorin accordance with an internet protocol (IP). At step 470, linkaggregator 26 determines a location for the relevant mobile device 50based on location data received from multiplexers 24. As noted above,this location may represent a location associated with the relevantmobile device 50 in any appropriate manner and having any appropriateform and precision.

After determining a location for the relevant mobile device 50, linkaggregator 26 may take additional steps to utilize the determinedlocation. For example, at step 480, link aggregator 26 may transmit tothe dispatcher's client a location response identifying the determinedlocation (e.g., an HTTP response that includes a latitude and longitudefor the relevant mobile device 50). The determined location may then bedisplayed to the dispatcher on a client monitor or otherwisecommunicated to the dispatcher. Additionally, at step 490, linkaggregator 26 may store the determined location to facilitate datarecovery or subsequent analysis of device locations. The operation ofintercept system 20 with respect to determining this particular locationmay then end as shown in FIG. 4.

Although the present invention has been described with severalembodiments, a myriad of changes, variations, alterations,transformations, and modifications may be suggested to one skilled inthe art, and it is intended that the present invention encompass suchchanges, variations, alterations, transformations, and modifications asfall within the scope of the appended claims.

1. A system for determining a location for a mobile communicationdevice, comprising: a plurality of taps, each tap comprising: a pair ofinline connectors operable to couple inline to a communication link of aradio access network and to pass between the inline connectors a signalreceived over the communication link; a multiplexer connector operableto couple the tap to a multiplexer; and a cable connecting themultiplexer connector to the pair of inline connectors, wherein thecorresponding tap is operable to replicate signals passing between thepair of inline connectors and to propagate the replicated signals alongthe cable to the multiplexer connector; the multiplexer, comprising: aplurality of tap interfaces, each tap interface operable to couple themultiplexer to one of the taps; a network interface operable to couplethe multiplexer to a data network; and a processor operable to: receive,from each tap, signals replicated by the tap; extract location data fromthe replicated signals, wherein the location data is associated with oneor more mobile devices operating in a geographic area served by theradio access network; and transmit the location data, in accordance withan internet protocol (IP), over the data network to a link aggregator;and the link aggregator, operable to: receive the location data from themultiplexer; and determine a location for one of the mobile devicesbased on the received location data.
 2. The system of claim 1, whereinthe plurality of taps comprise a first group of taps, the location datacomprises a first set of location data, and the multiplexer comprises afirst multiplexer coupled to the first group of taps, and furthercomprising: a second group of taps; and a second multiplexer operableto: receive, from each of the second group of taps, signals replicatedby that tap; extract a second set of location data from the signalsreplicated by the second group of taps; and transmit the second set oflocation data, in accordance with an internet protocol (IP), over thedata network to the link aggregator; and wherein the link aggregator isfurther operable to determine a location for one of the mobile devicesby determining the location based on the first set of location data andthe second set of location data.
 3. The system of claim 1, wherein theinline connectors of each tap are operable to couple inline to acommunication link of the radio access network by coupling inline to anAbis interface of the radio access network
 4. The system of claim 1,wherein the inline connectors of each tap are operable to couple inlineto a communication link of the radio access network by coupling inlineto an Iub interface of the radio access network
 5. The system of claim1, wherein the inline connectors of each tap are further operable topass a signal received over the communication link between the inlineconnectors without substantially reducing a signal level of the receivedsignal.
 6. The system of claim 1, wherein each of the taps is operableto replicate signals by passively replicating signals passing between acorresponding pair of inline connectors.
 7. The system of claim 1,wherein the processor is operable to extract location data from thereceived signals by extracting a cell global identify (CGI) from thereceived signals, and wherein the link aggregator is operable todetermine a location of one of the mobile devices based on the extractedCGI.
 8. The system of claim 1, wherein the multiplexer further comprisesone or more rack-mountable chassis, and wherein the processor, theplurality of tap interfaces, and the network interface are attached tothe one or more rack-mountable chassis.
 9. The system of claim 8,wherein the one or more rack-mountable chassis are less than four rackunits (4U) in total size.
 10. (canceled)
 11. (canceled)
 12. (canceled)13. (canceled)
 14. (canceled)
 15. (canceled)
 16. (canceled) 17.(canceled)
 18. (canceled)